Redoing this to be more clear:

Question

How can I call a function inside a module?

File: test.exs

defmodule MyModule do

  def sum(a, b) do
    a + b
  end

  MyModule.sum(1,1) # or sum(1,1)
end

elixir test.exs :

** (UndefinedFunctionError) function MyModule.sum2/2 is undefined (function not available)
    MyModule.sum2(1, 1)

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Original question asking same thing but more confused:
This is an .exs file used for Phoenix migrations, so it’s inside the folder /priv/repo/migrations. (In case that matters). I wrote a function but it’s totally blocked. I don’t want to import it from another module since this is where it goes (declared and used in same module)

defmodule MyApp.Repo.Migrations.MyModule do
  use Ecto.Migration

  def sum1(a, b) do #public
    a + b
  end
 defp sum2(a, b) do #private
    a + b
  end

end

From iex -S mix

iex(2)> MyApp.Repo.Migrations.MyModule
MyApp.Repo.Migrations.MyModule

iex(3)> MyApp.Repo.Migrations.MyModule.sum2
** (UndefinedFunctionError) function MyApp.Repo.Migrations.MyModule.sum2/0 is undefined (module MyApp.Repo.Migrations.MyModule is not available)
    MyApp.Repo.Migrations.MyModule.sum2()

iex(4)> MyApp.Repo.Migrations.MyModule.sum1(1,1)
** (UndefinedFunctionError) function MyApp.Repo.Migrations.MyModule.sum1/2 is undefined (module MyApp.Repo.Migrations.MyModule is not available)
    MyApp.Repo.Migrations.MyModule.sum1(1, 1)
    iex:4: (file)

If U can’t call it like this, this is what I want to do. It gives the same error as the above attempt.

defmodule MyApp.Repo.Migrations.MyModule do
  use Ecto.Migration

  def sum1(a, b) do
    a + b
  end
 defp sum2(a, b) do
    a + b
  end
IO.puts(sum1(1,1)) #or sum2(1,1)
end

Pls Ignore it being bad practice (if it is) to have a function in a migration file, unless this the cause.

Real use case (Not sure if this link is accessible to all?)